In the prior art, an electromagnetic induction type contactless power transmission device includes a metal detector to detect metal set on a setting surface on which an electric instrument is set to be supplied with power. The metal detector prevents the metal from being induction-heated when the electric instrument is supplied with power. Patent document 1 describes an example of a contactless power transmission device including a primary coil for supplying power and a detection coil for detecting metal. The contactless power transmission device excites the primary coil, which is for supplying power, to supply an electric instrument with power and excites the detection coil, which is for detecting metal, to detect metal or the electric instrument.